Arrangement for internal combustion engine

ABSTRACT

A sound-absorbing exhaust system for an internal combustion engine. The system may comprise a receptacle, an inlet which is arranged in the receptacle and through which exhaust gases can be directed into the same, and a discharge pipe, which connects the interior of the receptacle to the ambient air and through which exhaust gases can be discharged from the same. The discharge pipe may have, at its end positioned outside the receptacle, a seal, which substantially seals the discharge pipe at this end. The discharge pipe may have at least one, but also a plurality of radial holes, which are positioned outside the receptacle. The system may further include a sleeve, which wholly or partially surrounds the discharge pipe outside the receptacle. This arrangement may reduce the emission of exhaust gas noise from the system.

This U.S. nonprovisional application claims priority under 35 U.S.C. § 119 to Swedish Patent Application No. 0401554-1 filed Jun. 17, 2004, the contents of which are incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a sound-absorbing exhaust system for an internal combustion engine, said exhaust system comprising a receptacle, an inlet which is arranged in the receptacle and through which exhaust gases can be directed into the receptacle, and a discharge pipe, which connects the interior of the receptacle to the ambient air and through which exhaust gases can be discharged from the receptacle.

BACKGROUND ART

Sound-absorbing exhaust systems may be used for internal combustion engines of various types, for example smaller ones, which are used, for example, in mopeds, lawnmowers and the like.

The sound-absorbing exhaust system may serve to reduce the noise arising as exhaust gases leave the internal combustion engine, for the purpose of reducing acoustic nuisances.

SUMMARY OF THE INVENTION

Example embodiments of the present invention may provide a sound-absorbing exhaust system which reduces the noise emission from an internal combustion engine.

In an example embodiment, the present invention is directed to a sound-absorbing exhaust system for an internal combustion engine, said exhaust system comprising a receptacle, an inlet which is arranged in the receptacle and through which exhaust gases can be directed into the receptacle, and a discharge pipe, which connects the interior of the receptacle to the ambient air and through which exhaust gases can be discharged from the receptacle, wherein the discharge pipe at its end positioned outside the receptacle has a seal, which substantially seals the discharge pipe at this end, that the discharge pipe has at least one radial hole, which is positioned outside the receptacle, and that a sleeve wholly or partially surrounds the discharge pipe outside the receptacle.

In another example embodiment, the present invention may relate to a sound-absorbing exhaust system where the discharge pipe at its end positioned outside the receptacle has a seal, which substantially seals the discharge pipe at this end, where the discharge pipe has at least one radial hole, which is positioned outside the receptacle, and where a sleeve wholly or partially surrounds the discharge pipe outside the receptacle.

Such an arrangement may reduce the noise emission from an internal combustion engine. Tests have demonstrated that the exhaust gas noise from the engine may decrease by 3 dB. Moreover the frequency content of the remaining noise may be such that it is experienced as less “sharp”, and therefore the noise may be less disturbing.

The discharge pipe may have a plurality of radial holes, which are positioned outside the receptacle. Exhaust gases may be spread in the space between the discharge pipe and the sleeve in a suitable manner.

In an example embodiment, the seal may include a star crimp.

In an example embodiment, the sleeve may be attached to the receptacle, and may project from the receptacle to the same extent as does the discharge pipe, which may result in improved absorption.

In an example embodiment, the receptacle may be elongate in the longitudinal direction of the discharge pipe, and the discharge pipe may extend into the receptacle, at least along half the length of the receptacle.

The receptacle may be, in the longitudinal direction, divided into a plurality of chambers by one or more gas-permeable partitions. This may result in improved sound-absorption.

In an example embodiment, the discharge pipe may have at its end positioned in the receptacle a seal and a plurality of radial holes. Thus the discharge pipe may have the same design at both ends, which may be advantageous in terms of manufacture.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is a perspective view of a sound-absorbing exhaust system according to an example embodiment of the invention.

FIG. 2 is a schematic longitudinal section through the exhaust system in FIG. 1.

FIG. 3 shows the result of a comparison between a conventional exhaust system and an exhaust system according to an example embodiment of the invention.

DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 is a perspective view of a sound-absorbing exhaust system 1 according to an example embodiment of the invention. The exhaust system 1 may be adapted to be connected to an internal combustion engine and may include a receptacle 2 of welded sheet metal. The receptacle may define an inner space of a certain volume. An inlet 3 may be arranged in the receptacle 2, as shown with a connecting pipe. Exhaust gases from the internal combustion engine may be directed through the inlet 3 into the receptacle 2. The exhaust system 1 may further include a discharge pipe, which connects the interior of the receptacle 2 to the ambient air and through which exhaust gases can be discharged from the receptacle 2. Of the discharge pipe, FIG. 1 shows only an end, which is provided with a seal 5. That part of the discharge pipe which projects out of the receptacle is radially surrounded by an outer sleeve 7, which may be concentric with the discharge pipe. The sleeve 7 may be arranged so that a space is formed between the sleeve 7 and the discharge pipe, through which space exhaust gases can flow.

FIG. 2 is a schematic longitudinal section through the exhaust system in FIG. 1. FIG. 2 shows that the discharge pipe 4 may extend into the receptacle 2. In an example implementation, the discharge pipe may be about 40 cm long, have an outer diameter of 32 mm and a material thickness of 1.5 mm. At its end positioned outside the receptacle 2, the discharge pipe 4 may have, as mentioned above, a seal 5, which substantially seals the discharge pipe 4 at this end. “Substantially sealing” means that the seal 5 largely seals the discharge pipe 4, but that a certain degree of leakage through the seal 5 may be permitted. In an example embodiment, the seal 5 may be provided by what is commonly referred to as a star crimp, e.g. the outer end of the discharge pipe 4 may be folded so that a seal is provided. The star crimp is easy to provide and can be made in one operation. However, other ways of arranging the seal of the pipe are also interrelated; for example a sealing plate can be welded to the end of the pipe, or the end of the pipe can be threaded and sealed by a screw cap.

The discharge pipe 4 may have at least one, but also a plurality of, for example about 50, radial holes 6, distributed in three rows for example, which holes may be positioned outside the receptacle 2. The holes may be radial with regard to the longitudinal (axial) direction of the discharge pipe and may, for example, have a diameter of 3.5 mm. In an example embodiment, the discharge pipe 4 has also at the end positioned in the receptacle 2 a seal 15 and a plurality of radial holes 16. Thus both ends of the discharge pipe can have the same appearance. As shown, also the inner part of a discharge pipe 20 can be configured in the same way.

Outside the receptacle 2 the outer sleeve 7 may wholly or partially surrounds the discharge pipe 4 in the radial direction. In an example implementation, the sleeve may be 5 cm long and has an outer diameter of 5 cm. The sleeve 7 may be attached to the receptacle 2, for example welded to the same.

The sleeve 7 may project to about the same extent from the receptacle 2 as does the discharge pipe 4, but may also project longer or shorter. The sleeve 7 may give, together with the seal 5 and the radial holes 6, a pressure, pulse and/or flow equalising effect, which may reduce the noise level. These additional features may be provided at a relatively low cost.

The receptacle 2 may be elongate in the longitudinal direction of the discharge pipe 4. The discharge pipe 4 may extend into the receptacle 2, at least along half the length of the receptacle 2.

As is evident from FIG. 2, the receptacle may be divided in the longitudinal direction into a plurality of (for example, as shown, two) chambers 10, 11 by partitions 13 which may be gas permeable in various ways. In another example embodiment, the receptacle 2 may have three chambers.

FIG. 2 also illustrates an exhaust gas flow 19 through the exhaust system 1. The exhaust gases may enter the system through an inlet pipe 20, which may be inserted into the opening 3 of the receptacle 2. The exhaust gases may then reach, through a radial hole in the inlet pipe 20, a first chamber 10. Subsequently the exhaust gases may pass on to a second chamber 11 through a partition 13, which may be perforated. After that, the exhaust gases may pass into the discharge pipe 4 through radial holes 16 at the inner end thereof. The exhaust gas flow 19 may then follow the discharge pipe 4 and pass out of the same through the radial holes 6 at the outer end, to the space between the discharge pipe 4 and the surrounding sleeve 7. From this space, the exhaust gas flow 19 may reach the ambient air.

FIG. 3 shows the result of a comparison between a conventional exhaust system and an exhaust system modified according to an example embodiment of the present invention. The conventional system does not have the sleeve 7 in FIGS. 1-2, and the discharge pipe does not have the seal 5 at the outer end and the radial holes 6 outside the receptacle. Otherwise, the systems are similar. The graph in FIG. 3 shows the noise level at different frequency bands for the conventional system (dotted line) and for a system according to an example embodiment of the invention (solid line). The measurement at the distance 4 m relates to the exhaust gas noise only, because the actual engine (one-cylinder engine) has been made sound-insulated on the occasion of measurement.

On the whole, the noise level may be about 3 dB lower for the system according to an example embodiment of the present invention. In addition, the reduction may be achieved substantially in the range of 400 Hz-5 kHz, which gives a significantly less sharp and disturbing sound.

The invention is not limited to the example embodiments described above and can be varied within the scope of the appended claims. 

1. A sound-absorbing exhaust system for an internal combustion engine, said exhaust system comprising: a receptacle, an inlet which is arranged in the receptacle and through which exhaust gases can be directed into the receptacle, and a discharge pipe, which connects the interior of the receptacle to the ambient air and through which exhaust gases can be discharged from the receptacle, wherein the discharge pipe at its end positioned outside the receptacle has a seal, which substantially seals the discharge pipe at this end, that the discharge pipe has at least one radial hole, which is positioned outside the receptacle, and that a sleeve wholly or partially surrounds the discharge pipe outside the receptacle.
 2. A sound-absorbing exhaust system as claimed in claim 1, in which the discharge pipe has a plurality of radial holes, which are positioned outside the receptacle.
 3. A sound-absorbing exhaust system as claimed in claim 1, in which the seal includes a star crimp.
 4. A sound-absorbing exhaust system as claimed in claim 1, in which the sleeve is attached to the receptacle.
 5. A sound-absorbing exhaust system as claimed in claim 4, in which the sleeve projects from the receptacle to the same extent as does the discharge pipe.
 6. A sound-absorbing exhaust system as claimed in claim 1, in which the receptacle is elongate in the longitudinal direction of the discharge pipe, and the discharge pipe extends into the receptacle, at least along half the length of the receptacle.
 7. A sound-absorbing exhaust system as claimed in claim 6, in which the receptacle in the longitudinal direction is divided into a plurality of chambers by means of at least one gas-permeable partition.
 8. A sound-absorbing exhaust system as claimed in claim 1, in which the discharge pipe at its end positioned in the receptacle has a seal and a plurality of radial holes. 